(Solved) OpenCL and Detail Level

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Offline Voulxe

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« on: April 25, 2020, 06:53:58 PM »
Every now and then I observe that the Level of Detail, using OpenCL, is very low compared to CPU-Render.

Attached are two images, same scene except for OpenCL/CPU mode. Detail Level of 2 on a stock ABoxMod1 fractal.

Scene:
Code: [Select]
# Mandelbulber settings file
# version 2.21
# only modified parameters
[main_parameters]
ambient_occlusion 8;
ambient_occlusion_enabled true;
ambient_occlusion_mode 1;
background_3_colors_enable false;
background_color_1 7d00 7e00 7f00;
basic_fog_color 0000 0000 0000;
basic_fog_enabled true;
basic_fog_visibility 0,3259505927562714;
brightness 1,5;
camera 3,876883095372802 -2,572773299289402e-16 0,1459914988273803;
camera_distance_to_target 33,95761871949897;
camera_rotation 90 7,223477862333808 0;
camera_top 0,1257397579024516 -7,699339602040024e-18 0,992063260726166;
contrast 1,2;
DE_factor 0,359375;
detail_level 2;
DOF_blur_opacity 2;
DOF_focus 0,0004563603433780372;
DOF_max_noise 0,125;
DOF_MC_global_illumination true;
DOF_number_of_passes 4;
DOF_radius 2,5;
DOF_samples 800;
fake_lights_color ff00 c400 9300;
fake_lights_intensity 4;
fake_lights_max_iter 32;
fake_lights_min_iter 32;
fake_lights_orbit_trap_shape line;
fake_lights_visibility 2;
fake_lights_visibility_size 10;
file_lightmap /home/volker/mandelbulber/settings/textures/vx_01.jpg;
flight_last_to_render 0;
fog_color_1 0000 0000 0000;
fog_color_2 c100 a000 8a00;
fog_color_3 0000 0000 0000;
formula_1 64;
formula_material_id 3;
fov 33,4;
gamma 0,8;
glow_intensity 1,6;
hdr true;
image_height 1080;
image_width 1920;
julia_c -0,9407523226274576 -5,377447527993623 1,215466844146564;
julia_mode true;
keyframe_last_to_render 0;
main_light_alpha -168,69;
main_light_beta 56,82;
mat1_is_defined true;
mat1_reflectance 0,8;
mat1_rough_surface true;
mat1_surface_color 2b00 2400 1f00;
mat1_surface_color_gradient 0 fd6029 999 698403 1999 fff59b 2999 f5bd22 3999 0b5e87 5000 c68876 5999 a51c64 7000 3b9fee 7999 d4ffd4 9000 aba53c;
mat1_surface_gradient_enable false;
mat1_surface_roughness 0,125;
mat1_use_colors_from_palette false;
mat2_coloring_speed 4;
mat2_fractal_coloring_algorithm 4;
mat2_fresnel_reflectance true;
mat2_is_defined true;
mat2_metallic false;
mat2_reflectance 0,8;
mat2_specular 1;
mat2_specular_metallic 4;
mat2_specular_metallic_roughness 0,8;
mat2_specular_metallic_width 2;
mat2_specular_plastic_enable false;
mat2_surface_color_gradient 0 ddd174 3333 d15727 6666 101413;
mat3_coloring_speed 2;
mat3_fractal_coloring_ic_rad_enabled_false true;
mat3_fractal_coloring_ic_rad_weight 2;
mat3_fractal_coloring_ic_xyz_enabled_false true;
mat3_fractal_coloring_init_cond_enabled_false true;
mat3_fractal_coloring_xyzC_111 2 1 1;
mat3_is_defined true;
mat3_metallic false;
mat3_specular 1,26;
mat3_specular_plastic_enable false;
mat3_specular_width 1,6;
mat3_surface_color_gradient 0 fdfdfd 4938 131627;
mat3_surface_roughness 0,05;
MC_soft_shadows_enable true;
primitive_sphere_1_position 3,8 0,008 0,16;
primitive_sphere_1_radius 0,016;
reflections_max 2;
shadows_cone_angle 16;
SSAO_random_mode true;
target -29,81122285798924 1,979738932914707e-15 4,415814255560949;
view_distance_max 92,16685373568622;
volumetric_fog_colour_1_distance 0,01268509363849851;
volumetric_fog_colour_2_distance 0,05074037455399405;
volumetric_fog_distance_factor 0,05074037455399404;

How do I increase the detail output when using OpenCL?
Regards,
Voulxe

Linkback: https://fractalforums.org/mandelbulber/14/opencl-and-detail-level/3446/
« Last Edit: April 25, 2020, 08:12:25 PM by Voulxe »

Offline buddhi

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« Reply #1 on: April 25, 2020, 07:31:48 PM »
This problem is caused by single precision of OpenCL calculations (program for CPU uses double precision). When camera is too close to the object then program cannot calculate more detailed objects.
There a way how you can increase level of details for close objects but it can lead to visible noise or other artifacts on them. Go to Rendering Engine dock and enable option "Advanced quality settings". When it is enabled the minimum detail size is 1e-12 (by default in OpenCL mode is 1e-6). It will force to calculate more details but without guaranty of quality. In your case value 2e-7 should be optimal.

Offline Voulxe

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« Reply #2 on: April 25, 2020, 08:11:26 PM »
Thanks for the fast and helpful reply  :)


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